5
5.0

Sep 18, 2013
09/13

by
Gabor Csanyi; Gabor Domokos

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While static equilibria of flexible strings subject to various load types (gravity, hydrostatic pressure, Newtonian wind) is well understood textbook material, the combinations of the very same loads can give rise to complex spatial behaviour at the core of which is the unilateral material constraint prohibiting compressive loads. While the effects of such constraints have been explored in optimisation problems involving straight cables, the geometric complexity of physical configurations has...

Source: http://arxiv.org/abs/1209.1758v2

8
8.0

Sep 17, 2013
09/13

by
Gabor Csanyi; Balazs Szendroi

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We study a social network consisting of over $10^4$ individuals, with a degree distribution exhibiting two power scaling regimes separated by a critical degree $k_{\rm crit}$, and a power law relation between degree and local clustering. We introduce a growing random model based on a local interaction mechanism that reproduces all of the observed scaling features and their exponents. Our results lend strong support to the idea that several very different networks are simultenously present in...

Source: http://arxiv.org/abs/cond-mat/0305580v1

5
5.0

Sep 22, 2013
09/13

by
Gabor Csanyi; T. A. Arias

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We explore a new class of computationally feasible approximations of the two-body density matrix as a finite sum of tensor products of single-particle operators. Physical symmetries then uniquely determine the two-body matrix in terms of the one-body matrix. Representing dynamical correlation alone as a single tensor product results in a theory which predicts near zero dynamical correlation in the homogeneous electron gas at moderate to high densities. But, representing both dynamical and...

Source: http://arxiv.org/abs/cond-mat/9805388v4

13
13

Sep 22, 2013
09/13

by
Gabor Csanyi; T. A. Arias

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We identify the shortcomings of existing ab initio quantum chemistry calculations for the hyperfine couplings in the recently characterized azafullerene, C59N. Standard gaussian basis sets in the context of all--electron calculations are insufficient to resolve the spin density near the cores of the atoms. Using the Projector Augmented Wave method implemented on top of a standard pseudopotential plane--wave density--functional framework, we compute significantly more accurate values for the...

Source: http://arxiv.org/abs/cond-mat/0205198v1

5
5.0

Sep 22, 2013
09/13

by
Gabor Csanyi; Sohrab Ismail-Beigi; T. A. Arias

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Based on ab initio calculation, we propose a new structure for the fundamental excitation of the reconstructed 30$^\circ$ partial dislocation in silicon. This soliton has a rare structure involving a five-fold coordinated atom near the dislocation core. The unique electronic structure of this defect is consistent with the electron spin resonance signature of the hitherto enigmatic thermally stable R center of plastically deformed silicon. This identification suggests the possibility of an...

Source: http://arxiv.org/abs/cond-mat/9805328v1

22
22

Sep 18, 2013
09/13

by
Gabor Csanyi; Chris J. Pickard; B. D. Simons; R. J. Needs

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Motivated by recent experimental work, we use first-principles density functional theory methods to conduct an extensive search for low enthalpy structures of C$_6$Ca under pressure. As well as a range of buckled structures, which are energetically competitive over an intermediate range of pressures, we show that the high pressure system ($\gtrsim 18$ GPa) is unstable towards the formation of a novel class of layered structures, with the most stable compound involving carbon sheets containing...

Source: http://arxiv.org/abs/cond-mat/0611511v1

12
12

Sep 22, 2013
09/13

by
Gabor Csanyi; Torkel D. Engeness; Sohrab Ismail-Beigi; T. A. Arias

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Based on {\em ab initio} calculation, we propose a new structure for the fundamental excitation of the reconstructed 30$^\circ$ partial dislocation in silicon. This soliton has a rare structure involving a five-fold coordinated atom near the dislocation core. The unique electronic structure of this defect is consistent with the electron spin resonance signature of the hitherto enigmatic thermally stable R center of plastically deformed silicon. We present the first {\em ab initio} determination...

Source: http://arxiv.org/abs/cond-mat/0011147v1

19
19

Jul 24, 2013
07/13

by
Daniel J. Cole; Mike C. Payne; Gabor Csanyi; S. Mark Spearing; L. Colombi Ciacchi

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We have developed a classical two- and three-body interaction potential to simulate the hydroxylated, natively oxidised Si surface in contact with water solutions, based on the combination and extension of the Stillinger-Weber potential and of a potential originally developed to simulate SiO2 polymorphs. The potential parameters are chosen to reproduce the structure, charge distribution, tensile surface stress and interactions with single water molecules of a natively oxidised Si surface model...

Source: http://arxiv.org/abs/0807.3215v1

20
20

Sep 22, 2013
09/13

by
Albert P. Bartok; Michael J. Gillan; Frederick R. Manby; Gabor Csanyi

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We show how machine learning techniques based on Bayesian inference can be used to reach new levels of realism in the computer simulation of molecular materials, focusing here on water. We train our machine-learning algorithm using accurate, correlated quantum chemistry, and predict energies and forces in molecular aggregates ranging from clusters to solid and liquid phases. The widely used electronic-structure methods based on density-functional theory (DFT) give poor accuracy for molecular...

Source: http://arxiv.org/abs/1302.5680v1